1. Field of the Invention
The disclosure relates to a liquid crystal display, and more particularly, to a liquid crystal display having photo-sensing input mechanism.
2. Description of the Prior Art
Along with the requirement of a friendly communication interface for a user to interact with an electronic device, an input-type display device for controlling operations of the electronic device, instead of using a keyboard or a mouse, has steadily become the mainstream, thereby making application of input-type display devices increasingly widespread. The input mechanisms of the input-type display devices are primarily classified into the photo-sensing input mechanism and the touch-sensing input mechanism. Since the display device with the touch-sensing input mechanism is likely to be damaged by frequent touch action, the lifetime of the display device with the photo-sensing input mechanism is normally greater than that of the display device with the touch-sensing input mechanism. In general, the photocurrent/bias-voltage characteristic curve of a photo-sensing transistor used in the photo-sensing input mechanism is changing following a change of incident light intensity. Under fixed bias voltage, the photocurrent increase as the incident light intensity increases, which is employed to perform an input sensing operation. For instance, a first photocurrent generated in response to a first incident light intensity can be used to indicate a first input state, and a second photocurrent generated in response to a second incident light intensity lower than the first incident light intensity can be used to indicate a second input state. The first photocurrent is greater than a predetermined threshold and the second photocurrent is less than the predetermined threshold. However, the aforementioned photocurrent/bias-voltage characteristic curve may be shifted due to long-term bias/irradiation operation, and the photocurrent corresponding to the same bias voltage and the same incident light intensity is growing as the bias/irradiation operation proceeds. That is, after long-term bias/irradiation operation, the second photocurrent may be greater than the predetermined threshold, which in turn causes input state misjudgment and results in malfunction of backend circuit.